In mechanical watches, the energy is generally provided by springs wound in a spiral and housed in barrels. Depending on the case, one seeks to obtain the maximum amount of energy in a given volume in order to optimize the transmitted torque and the power reserve, i.e., the maximum duration during which the barrel can cause the movement to operate under correct conditions. These parameters are theoretically improved by increasing the height of the coils (i.e., the dimension perpendicular to the plane of the spiral) and decreasing the thickness of the blade making up the spiral, allowing a larger number of coils for a barrel with a constant diameter. However, the manufacturing constraints of the springs quickly limit the possibilities for increasing the height or reducing the thickness.
It has already been proposed, in the state of the art, to associate several barrels, either in parallel or in series, in order to improve the transmitted torque or the power reserve. For example, document U.S. Pat. No. 4,363,553 proposes a construction in which two barrels, each containing a spring, are assembled in series.
The present invention aims to propose an alternative and advantageous construction, making it possible to improve the energy performance of a barrel in a limited bulk.